Anti-Freezing Pavement Using Hot Rolled Asphalt Technology

N. Inaba & K. Yamada, T. SanpeiNIPPO CORPORATION, Chuo-ku, Tokyo, Japan

ABSTRACT: Anti-freezing pavements with rubber particles and those with chemicalmaterials were introduced from Europe and have been widely constructed in Japan since the1980’s. However, the anti-freezing pavements with rubber particles have less durabilitybecause they incorporate soft materials in their whole surface course layer. The anti-freezingpavements with chemical materials will lose their effect in process of time. To solve theseproblems, we developed a new type of anti-freezing pavement with physically flexiblematerials, the Gum Rolled Asphalt. It is a kind of hot rolled asphalt pavement in which specialsynthetic rubber aggregates are used for chipping. As the synthetic rubber aggregates cannotadhere to ice easily, the anti-freezing function of the Gum Rolled Asphalt can be achievedthrough promoting the flaking off of the ice layer on the aggregates which have been crushedby passing vehicles. In the paper, we describe the details of the pavement, includinganti-freezing details of design and a recent application to national highway.

KEY WORDS: Rubber aggregate, design, development, construction

1. INTRODUCTION

In Japan from 1992, in order to prevent health hazards from dust caused by studded tireswearing out the pavement, the use of studded tires on vehicles has been restricted. Since thattime, the studless tire has replaced the studded tire. However, in order to assure traffic safety,lower road maintenance cost, and preserve the roadside environment (i.e. reduce the usage ofchloride), etc., anti-freezing pavements have been utilized.

From the latter half of the 1970s, anti-freezing pavement with physically flexible materials,meaning pavement composite with rubber particles have been introduced. Anti-freezingpavement with rubber particles is pavement using hot asphalt mixture with rubber particlesadded. The anti-freezing function is to transform the overall thickness of the surface course bythe stress caused by the traffic load, which increases stress in the ice on the pavement,eventually forming cracks in the ice. After the cracks form, the ice on the pavement surfacewhere rubber particles are exposed will be exfoliated from the surface, because the adherentstrength of rubber and ice is less than that of the asphalt and ice.

Increasing the amount of rubber particles mixed in the asphalt mixture enlarges thedeflection amount of the surface course and the anti freezing effect becomes greater. However,if too much rubber particles are mixed, it becomes difficult to compact the hot asphalt mixture,and the strength and durability of the pavement is significantly lowered.

Anti-freezing pavement with rubber aggregate was developed in 1994 for the purpose ofincreasing the anti-freezing effect and insuring the stability of the asphalt mixture foranti-freezing pavement. In the pavement, rubber aggregates of the equivalent size of 20 mm

are used. This pavement is constructed with rolling chipping rubber aggregates on the spreadhot asphalt mixture, to construct the surface where rubber aggregates are exposed. Thispavement does not use rubber particles but uses rubber aggregates, and does not distribute therubber aggregates into the asphalt mixture but exposes them to the surface of the pavement.(See Figure 1)

Figure 1: Conceptual diagram of Gum-Rolled asphalt

The English word “rubber” is pronounced [ɡɔmu] in Japanese. Therefore, we are callingthe construction of anti-freezing pavements with rubber aggregates, “Gum-Rolled asphalt.”

Details of design and the introduction of some features and a recent application are shownas follows.

2. DESIGN

2.1 Base Asphalt Mixture

The Gum-Rolled method uses the surface course of the asphalt pavement. It has the samestandard 5 cm thickness of the typical surface course in Japan. The binder using of the baseasphalt mixture is made of a large proportion of polymer-modified asphalt type II inconsideration of its fluidity resistance and its aggregate grip strength. However in the case ofa relatively lower traffic volume, the use of petroleum asphalt penetration 40-60 is also used.Moreover, the aggregate and filler meet the quality standard listed in the Handbook ofPavement Construction (Table 1).

Table 1: Quality standard of materials

Material Quality standardPolymer-modified asphalt Type IIPetroleum asphalt for road 40～60

Course aggregate・Fine Aggregate・filler

Standard properties or quality standarddescribed in the Handbook of PavementConstruction (the Japan Road Association)

Table 2 shows an example of a base asphalt mixture. Table 3 shows the properties of themixture in which a binder uses polymer-modified asphalt type II.

Road roller

Rubber aggregate MMA resin

Anti-skid aggregate

Base asphalt mixture

Table 2 Mixing example of base asphalt mixture

Materials Design Ratio（％）Single-sized crushed Stone S-20(grade-6)Single-sized crushed Stone S-13(grade-5)

Fine sandMineral filler

20205010

Asphalt 7.0-9.0

Table 3: Example of properties of Marshall test

density(g/cm3)

Air Void(％)

Degree of saturation(％)

Marshall stability(kN)

flow value(1/100cm)

2.3203.7

（3～7）82.0

（70～85）9.73

（4.9以上）

47(20～50)

（）:Target Value

3.2 Rubber Aggregate

1) Specification

Table 4 shows the specifications of the rubber aggregate used in the Gum-Rolled asphalt.

Table 4: Specification of rubber aggregate

Item Specification Remarks

Shape Special pentagonal prism

Diagonal length D (mm) 20.0±2.0

Length L (mm) 22.0±5.0Ruggedness Length

S (mm)2.0±1.0

MaterialSBR special rubber

The recycled rubber powder is used for part.

Hardness of rubber70-90

JIS K 6301(A Sclerometer)

D

L

S

Note: The rubber aggregate is pre-coated with straight asphalt or modified asphalt emulsion.

2) Shape

The rubber aggregate is shaped in the form of a pentagonal prism. In the early development ofGum-Rolled asphalt, the adhesion of the rubber with asphalt was not sufficient and there wasconcern that the rubber aggregate would exfoliate and be scattered when subjected to theforce of passing vehicles. Various shapes were used testing the fretting resistance and area ofexposure of each shape. After a comprehensive evaluation, the shape adopted was one thatapproximates that of a pentagonal prism (Kasahara, 1997). (See Figure 2)

Cuboids

Like pentagonal prisms

Like cylinders

Ex

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Are

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Ag

gre

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Nar

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Wid

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Pullout Resistance

Weak Strong

Figure 2: Relation between pullout resistance and exposure area of rubber aggregate

3) Material

In the development stage the chosen rubber material consisted of EPDM (ethylene propylenerubber) in consideration of its weather proofing qualities. However, because there was aproblem with the rubber hardness and anti-wearing qualities of EPDM, SBR(styrene-butadiene rubber) was instead chosen for usage. Table 5 shows a comparison table ofthe two types of material. Because it has been acknowledged that SBR can be improved to beapproximately 3 times harder and flexible than EPDM which therefore has greater workabilityin a test construction, SBR (consisting of partially recycled rubber) is used.

Table 5: Comparison table of rubber material

Main raw material EPDM SBR Test methodsSpecific gravity 1.30 1.35 JIS K6301

Hardness 84-88 80-86 JIS Hardness(A)JIS Hardness Meter

Modulus of Elasticity(Theory value) About 5MPa About 4MPa Calculated from Hardness

Performance embedded Good Good PracticeWear resistance Better good JIS K6264Remarks

Weather proofing Good Better JIS K6266

3.3 Chipping Amount of Rubber Aggregates

The chipping amount of rubber aggregates have been set from 1.6～2.0kg/m2, however theyare mostly around 2.0kg/m2. We shall present the examination used in order to determine thevolume of the chipping rubber aggregate (Inaba, 2006).

1) Anti-Freezing Mechanism of Gum Rolled Asphalt

The supposition of anti-freezing mechanism of Gum Rolled is shown in figure 3. Due to theweight load of passing vehicles, bending failure of the ice between the rubber aggregatesoccurs. The ice is crushed by repeated load and scattered which partially exposes the road

surface. Remaining ice is likewise compressed, impacted and broken up by friction graduallyexposing the road surface.

1.Bending Failure 2. Partially Exposed 3. Compression Failure 4. Exposed

Figure 3 Assumption Mechanism of Anti-freezing

2) Range of Bending Failure

Figure 4 shows a supposition of the FEM model. Using the wheel load of a large commercialtruck, a stress analysis on the analysis range (½ the width from the center of a rubberaggregate), of the ice surface was conducted. The load range of the position of passing tireswas considered to be random, and the area of the rubber aggregates was ½. In an actual trafficthere would be different multiple repeated loads but this analysis presents the results of asingle load.

In figure 5, the distance between the rubber aggregates and the tensile failure stress of iceat 1.0MPa (Maeno, 1986) at the center of the rubber aggregates is plotted showing as thefailure point. According to figure 5, if the distance between the rubber aggregates laid on theroad surface is within 65mm, it was determined that the tensile strength would cause anoverall breaking up of the ice. If the distance between the rubber aggregates is 85mm, a 32.5mm distance between the centers of the adjoining rubber aggregates would result in a bendingfailure leaving an 85-32.5×2≒20mm size chip of ice in the center.

Figure 4 Analytical FEM model

0.35,MPa00010 ,E

4d

2N/mm80.P

350MPa4 ., E

350MPa0004 .,, E

mm5

mm10

mm20

mm50

aggregatesrubberbetweendistancetheofhalf2d

surfacemixtureasphalt

axiallyXrestrained:sidethe

axiallyYandaxiallyXrestrained:bottomthe

surfacefreezing

aggregaterubber

X

Y

Distance between rubberaggregates (mm)

Dis

tan

cefr

om

cen

ter

of

rub

ber

agg

reg

ate

(mm

)

1020 40 60 80 100

20

30

40

50

Bending failure range

65

Figure 5: Range of freezing bending failure

3) Compression Failure

The impact of a passing tire over a chip of ice on the road surface is also considered. Howevera study to calculate the area of the ice broken up was conducted using working compressiononly. The area of ice lump ( A ), with a wheel load of a passenger car at 2.500kN and thecompression failure stress of 6,000kN/m2 (Maeno, 1986), our equation is:

22 m0004206,000kN/mkN52 .. A

If the ice chip is a circle, the diameter would be 23 millimeters.In the case of bending failure, figure 5 assumes the wheel load of a large truck. A certain

amount of wheel load is needed; however the compression failure of a chip of ice is accordingto the size of the chip and will occur even with a passenger car.

4) Conclusion of Consideration

According to the area of bending failure and compression failure as stated in the aboveparagraphs, it was decided that the appropriate distance of the rubber aggregates should be85mm. (The bending failure distance with a large vehicle at 32.5mm×2 and the compressionfailure of a passenger car at 23mm.) The distance of such rubber aggregates shown at1.6kg/m2. 1.8～2.0kg/m2 of the chipping amount was adopted for the design value. Thischipping amount is calculated with the consideration of the bending failure caused by a largevehicle. The construction experience of a route with a lower traffic volume uses a chippingamount of approximately 2.5kg/m2.

3. ADVANTAGE

The characteristics of the Gum Rolled method are shown below.

1) A frozen surface is hard to occur. (Photograph 1)

The size of the rubber aggregate is large, and the shape of the rubber aggregates greatlydeform with the passing traffic, moreover, the area affected is wide which makes it easy to

break apart the freezing layer.It is difficult for snow to freeze and the freezing layer is easily exfoliated on the exposure

area of a large surface course of a pavement consisting of rubber aggregates of low bondstrength.

一一一般般般舗舗舗装装装

ゴゴゴムムムロロローーールルルドドド

ゴゴゴムムムロロローーールルルドドド

一一一般般般舗舗舗装装装

DDeennssee--ggrraaddeedd aasspphhaalltt

GGuumm RRoolllleedd

GGuumm RRoolllleedd

DDeennssee--ggrraaddeedd aasspphhaalltt

Photograph 1: Comparison between Gum-Rolled and normal pavement with snow

2) The continuation of the Effect

In the case of anti-freezing pavement made with chemical materials, the anti-freezing effect islowered with the elution of chloride in the pavement. However, because Gum-Rolled asphaltpavements use anti-freezing pavement with physically flexible material, the anti-freezingeffect continues throughout the pavement’s life.

3) High Durability

Due to the structure of the rubber aggregate scattered close to the surface course, comparedwith the type that uses a mixture of rubber particles, difficulty of rolling does not occur, andenough degree of compaction required for the asphalt mixture can be obtained.

4) Protecting the Environment

Gum Rolled asphalt does not require chloride spraying in the winter. This preserves theroadside environment.

4. A RECENT CONSTRUCTION EXAMPLE

4.1 The Construction Site

Here is an introduction of the application on an expressway where the design speed is 80km/h. The area is the Shitosake Toge Road in the mountainous region of Tottori Prefecture(which crosses 86.5 km of the central section of the Chugoku Transversal Expressway asshown in Figure 6.) The yearly cumulative snowfall is forecast at more than 3 meters. Thecommon measure of removing snow and ice on the expressway is to employ the spraying of asnow melting agent and the use of snow removal equipment. However, in order to avoid theuse of chloride which pollutes the roadside environment and to lower maintenance costs, theapplication of Gum-Rolled asphalt with anti-freezing pavement with physically flexiblematerials was employed.

Figure 6: Location map

4.2 Construction Overview

As shown in the construction overview table below, Gum Rolled asphalt was applied to1,147m of the main line ramp and 2,094m of the access road.

Table 6: Construction overview

Name of WorksShitosaka Toge Road ChizuPavement Works

Shitosaka Toge Road Chizu 2Pavement Works

Construction Period 16.3.2007 -22.12.2007 26.6.2007.6.26-13.3.2008Total 12,410m2 9,820m2

Earthwork Main line & ramp: 9,320m2 Main line &acces:5,480m2Gum-RolledArea

Bridge Main line:3,090m2 Main line &acces:4,340m2

width pavement width =7m(3.5m2)

4.3 Construction Process

The construction process using Gum Rolled asphalt is the same method as that of constructingrolled asphalt pavement. The base asphalt mixture is spread with the use of an asphalt paver.The rubber aggregates are chipped and spread over the asphalt surface mainly using avibrating roller with the chipping device in front of it. As the rubber aggregates are chipped

Tottori

Okayama

Hyogo

Chugoku Longitudinal Expressway

Chu

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ssw

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m

To

tto

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xp

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way

Har

ima

Exp

ress

way

Shitosaka-Toge Road

San-in Expressway

Chizu IC

Nishi Awakura IC

Chizu Minami IC

18.4km

Harima JCT

Service section

Under construction

and spread over the hot asphalt mixture, they are simultaneously rolled into the asphalt bysteel wheels of a vibrating roller. Finally, intermediate rolling of the pavement is conductedwith a pneumatic tire roller.

Photograph 2 shows the construction status of a bridge section. In the case of an earthworksection, normal size rubber aggregate is used. But on a bridge surface because the asphaltmixture is designed to be laid at a thickness of 4cm, a special size rubber aggregate (L=18mm,D=16mm）is used. The chipping amount of the special rubber aggregate is set to be the sameexposure area as that of a standard rubber aggregate.

Because the season of the construction site is autumn, the measure to account for atemperature drop of the hot asphalt mixture is to add an additive for warm mix asphalt at3kg/ton. This assures the easy rolling of the rubber aggregates.

Spreading Chipping and breakdown rolling Intermediate rolling

Photograph 2: Paving of Gum Rolled asphalt

Surface dressing using MMA (Methacrylic) resin is implemented to suppress scattering therubber aggregates by the action of snow removal equipment in winter. In this construction, theundercoating is done by a rubber rake and brush rollers, and a spray gun is used for the topcoating. It was determined by pre-construction testing to use an undercoating of 0.3kg/m2 ofMMA resin and a top coating of 0.2kg/m2 of MMA resin and a dispersion amount of 0.6kg/m2

of anti-skid fine aggregate.

Undercoat Spraying anti-skid aggregate Top coating

Photograph 3: Surface dressing using MMA resin

4.4 State of Usage

The photograph 4(a) shows a road during snow season. You can see that the passage ofvehicles melt the snow. Photo (b) is an enlargement of the surface of Gum-rolled asphalt.Photo (c) was taken during the same time slot as photo (b) showing the condition ofdense-graded asphalt concrete. The snow in photo (b) has become slush but in photo (c) it hasfrozen solid on the pavement. One winter has passed since the opening of the road but the

scatteration of the rubber aggregates seen on a curve of the road is minimal, and the overallroad condition is satisfactory. Moreover, because there have been no traffic accidents causedby freezing since the road opening, the anti-freezing effect is considered to be demonstrated(Ando, 2009).

(a) Surface after snow (Gum-Rolled) (b) Gum-Rolled (c) Dense-graded asphalt

Photograph 4: Snow on the pavement

5. IN CONCLUSIONThe difficult task of the full fledged application of the Gum-rolled construction process,firstly to an expressway and then to a normal road, has been solved by implementation of asingle improvement of the process.

We strive for ever better quality to improve the durability and performance of roadpavement as well as effectively lowering the winter road maintenance costs by theGum-rolled construction method.

REFERENCES

Ando, M., 2009. Application example to expressway in anti-freezing pavement. Proceedingsof the 11th Hokuriku Road Conference, Niigata, Japan

Kasahara, A., 1997. Development of Gum-Rolled asphalt pavement and application examples.Pavement No 32-9, Japan

Inaba, N., 2006. About the consideration and the countermeasure of Gum-Rolled. Proceedingsof the 10th Hokuriku Road Conference, Niigata, Japan

Maeno, N., 1986. Course of Basic Snow and Ice Vol.1 Structure and physical properties ofsnow and ice. Kokon Shoin, Japan